Scientists have identified a weird mass found off California.

Scientists have confirmed the finding of a strange, elusive creature that hasn't been conclusively seen since it was first described in 1900.

The mysterious, blob-like animal was collected by a remotely operated vehicle deep in California's Monterey Bay by scientists at the Monterey Bay Aquarium Research Institute. The translucent, tadpole-shaped creature itself is about three and a half inches long.

However, the animal was surrounded by a "house" of protein and cellulose that was several feet across. A type of larvacean, the creature produces these disposable houses to trap tiny food particles in the water and filter them inward. When the house's filters get clogged, the animal discards it and forms a new one, sometimes in a matter of hours. (See another mysterious blob.)

And although three and a half inches might sound small, it's actually giant for this type of animal. The sea squirt relatives are normally less than half an inch long, yet they play an important role in the ocean by transporting nutrients down into the deep sea (especially as they dispose of their spent houses).

Scientists have now confirmed that the creature is a second sighting of the species Bathochordaeus charon, named for the mythical Greek ferryman who was thought to transport souls of the dead across the River Styx. The first sighting of the animal was described in a 1900 paper and was based on a specimen found in the 1890s.

The elusive creature was possibly sighted on radar in past years, but scientists struggled to see one up close, leading some to question if the animal still lived or even existed at all. Perhaps it was simply a variant of another related species, some thought.

But then researchers saw one on the screen during a dive of the ROV Ventana. They directed the submersible to catch the soft animal in a net, which can be a tricky task. But once they got it to the surface, they realized that it matched the 1900 description of the species Bathochordaeus charon perfectly. (See photos of colossal sea creatures.)

"This is a nice discovery, and the paper says that they have genetic evidence distinguishing this species from a close congener," says Alice Alldredge, a biology professor at the University of California, Santa Barbara, who is familiar with the organism but not affiliated with the study.

"It also supports the importance of direct observation in studying the ocean," she adds.

In going back over their video archive from other missions, the scientists identified 12 more animals that they think are likely also the same species.